The present invention is based upon well-known magnetic ink character recognition (MICR) technology, but employs the technology in a manner so as to enable the encoding of data using the magnetic marking material within text characters, or portions thereof, and similar symbols or aspects of a document. The advantages of the present invention is that it provides a method to produce an encoded document, where the encoding or “watermark” is visually undetectable, but adequate to indicate authenticity of the document.
Heretofore, a number of patents and publications have disclosed magnetic ink character recognition devices and technology. The following patents are hereby incorporated by reference in their entirety, and the relevant portions may be briefly summarized as follows:
U.S. Pat. No. 4,901,114 to Parker et al., for “TRI LEVEL XEROGRAPHY USING A MICR TONER IN COMBINATION WITH A NON-MICR TONER,” issued Feb. 13, 1990, teaches single-pass tri-level xerography employed in an electronic printer to superimpose, with perfect registration, two images, one of which is printed with magnetic (MICR) toner, and the other of which is printed with non-magnetic toner. This permits the MICR toner to be used to print only those parts of the image that are necessary for the magnetic ink character recognition system to read the encoded information;
U.S. Pat. No. 5,147,744 to Sacripante et al. for “MICR PROCESSES WITH COLORED ENCAPSULATED COMPOSITIONS,” issued Sep. 15, 1992 discloses colored magnetic encapsulated (MICR) toner compositions, including those comprised of a core of polymer binder, a color pigment or dye, metal magnetic material, and a whitener, and thereover a polymeric shell prepared, for example, by interfacial polymerization and wherein the shell can have incorporated therein, thereon, or combinations thereof certain conductive metal oxide powders; and
U.S. Pat. No. 5,414,783 to Bov, Jr. et al. for a “WRITE HEAD FOR A MICR READER HAVING AN ADJUSTABLE FIELD PROFILE,” issued May 9, 1995, teaches improvements in apparatus and methods for recognizing characters printed in magnetic ink on documents.
Conventional watermarking methods typically work on grayscale or color images; they modify the grayscale or color of the image in some fashion. Such methods, besides lacking robustness when the document is printed, are awkward in dealing with black and white text documents where the pixel value is either 1 or 0. Other methods, such as shifting the characters are not robust and may carry very little load. Printing yellow dots has been applied in color hardcopies. Such methods rely on the assumption that the paper used is white, if a colored paper is used, or the paper has colored texture or colored designs, the small yellow dots can no longer be detected. Although the yellow dots are easily duplicated using regular inkjet printers, and easily detected using a blue filter, it is, nonetheless, useful in some applications.
In order to provide traceability or the ability to authenticate black and white text documents, the present invention “hides” or encodes information in the printed image. Hiding information may also be useful for other applications, such as usage rights control. Conventional digital watermarking methods are awkward in dealing with this kind of documents. We propose a method and a complete system to put magnetic watermarks in black symbols.
In accordance with the present invention, there is provided a text document authentication method, comprising the steps of: creating a document, where said document has text thereon; creating at least a portion of the text thereon with a combination of marking materials, including a first, visually perceptible marking material and a second, visually perceptible material, wherein the second marking material further includes a detectable, yet not visually perceptible, characteristic so as to be distinguishable from the first marking material with an aid, and where placement of the second marking material is indistinguishable to the unaided eye, yet is in a predefined pattern signifying the authenticity of the document containing such a pattern; and reading the second marking material pattern, with the aid, so as to verify the authenticity of the document, said reading step being sensitive to the presence of the detectable characteristic of the second marking material so as to identify the predefined pattern.
In accordance with another aspect of the present invention, there is provided a method for text document authentication, comprising the steps of: encoding a text image by analyzing the image to identify regions thereof suitable for rendering with a magnetic marking material, and indicating such areas in a digital document; writing the digital document using at least two different marking materials, one of which is a magnetic material, to render text on a marking medium; subsequently reading, from the marking medium, regions having magnetic material therein and sensing the relative strength of such regions so as to determine if such regions exhibit high or low magnetic fields; and based upon the strength of the fields, and the sequence thereof, decoding the signals so as to extract digital data represented by the magnetic marking material.
In accordance with yet another aspect of the present invention, there is provided a system for magnetically watermarking a text document for authentication, comprising: an encoder, operating on a digital text document to analyze the document to identify text regions thereof suitable for rendering with a magnetic marking material, and indicating such areas in the digital document; an image output device suitable for writing the digital document using at least two marking materials, one of which exhibits magnetic characteristics, so as to render the document on a marking medium, wherein regions of the text on said document are rendered with magnetic marking material and exhibit one of at least two levels of magnetic fields so as to provide an encoded magnetic mark within the text; a reader for sensing, on the marking medium, those text regions having magnetic material therein and sensing the relative strength of such regions so as to determine if such regions exhibit at least a high and a low magnetic field strength; and a decoder, for receiving a sequence of high and low magnet field strength signals from the reader and decoding the sequence of signals so as to extract digital data represented by the magnetic marking material.
One aspect of the invention is based on the discovery of a technique to enable the traceability or verification of the authenticity of text documents. Often, such documents are in traditional black and white, or at least the text therein is black and white. The techniques of the present invention utilize the text image areas to “hide” or embed information in the printed document through the use of magnetic inks, toners or similar marking materials. Such materials may be employed to print particular portions of certain characters so as to provide a magnetic mark on the characters, where the sequence of the marks, or the presence of marks may indicate further information relative to the document. In other words, the magnetic marks may provide “hidden” data serving to authenticate the document. A system implementing the invention would include an encoder and writer or printer on the one hand, and a scanner or similar reader and decoder on the other hand. The technique described above is advantageous because it is efficient and less detectable compared to other approaches of document authentication. The techniques can be adapted to any of a number of document types. As a result of the invention, it is possible to employ known technology to produce watermarked or self-authenticating documents.
The present invention will be described in connection with a preferred embodiment, however, it will be understood that there is no intent to limit the invention to the embodiment described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.